104. maximum depth of binary tree

class Solution {
public:
    int (TreeNode* root) {
        if (root == NULL)
            return 0;
        return max(maxDepth(root->left),maxDepth(root->right)) + 1;
    }
};

class Solution {
public:
    int (TreeNode *root)
    {
        if (root == NULL)
            return 0;
            
        queue<TreeNode *> p;
        p.push(root);
        int depth = 0;
        while (!p.empty())
        {
            depth++;
            int count = p.size();
            for (int i = 0; i < count; i++)
            {
                TreeNode *tmp = p.front();
                if (tmp->left != NULL)
                    p.push(tmp->left);
                
                if (tmp->right != NULL)
                    p.push(tmp->right);
                p.pop();
            }
            
        }
        return depth;
    }
};